With the rapid development of communication technology, information exchange among people appears more and more frequently. A single mobile phone may not meet the needs of people, especially those engaged in marketing or management, who may have to carry two or more mobile phones to meet the communication requirements, which brings inconvenience. Nowadays, multi-SIM multi-standby communication devices are emerging, which makes a user only need to carry one communication device with more than one Subscriber Identity Module (SIM) card or more than one User Identity Mode (UIM) card. It is far more convenient than the conventional way to carry several mobile phones.
Globe System of Mobile Communication (GSM) is one of the most widely used mobile communication systems. In general, if a subscriber wants to use multiple phone numbers in a single device in GSM system, the following solutions may be employed.
Firstly, a multi-SIM single-standby communication device may be used. In this communication device, there is more than one SIM card simultaneously, however, only one SIM card can be set in a standby state at a same time, and switching among the multiple SIM cards is executed by hardware circuits, which is generally selected when the device is powered on. Due to the effect of a protocol stack, the switching among the multiple SIM cards can not be executed dynamically when the communication device is in operation. For this matter, the mobile phone system needs to be rebooted (mainly reboot protocol stack/upper-layer software) to switch among the multiple SIM cards.
Secondly, a multi-SIM multi-standby communication device may be used to overcome the disadvantages in the multi-SIM single-standby communication device, in which multiple SIM cards can be standby simultaneously just like carrying multiple mobile phones, thereby improving practical application greatly.
An early multi-SIM multi-standby communication device actually possesses multiple sets of systems, generally two, each of which has a radio frequency module, a base band module, and a protocol stack respectively. The communication device having multiple systems can realize multiple SIM cards respectively in standby or communicating state, which is also referred to as a multi-SIM multi-standby multi-communicating communication device. However, this kind of communication device, with multiple systems utilized, suffers an additional cost and power consumption, and an increased size, which causes inconvenience. In view of radio frequency modules, allowing for co-channel interferences, one radio frequency (Rf) module is generally configured at the top of a mobile phone, and the other at the end of the mobile phone, so as to reduce interferences. Generally, the distance between the two antennae is greater than 100 mm.
Later multi-SIM multi-standby mobile phone is a kind of multi-SIM multi-standby single-communicating communication device, which uses only one set of communication module, including such as a radio frequency module and a base band module, compared to the early multiple systems. Because the upper protocol stacks needs to cooperate, the protocol stacks which operate independently in the early multi-SIM multi-standby multi-communicating communication device needs a close integration. Although the practical operation becomes more complicated, the multi-SIM multi-standby function may be achieved. Generally, multiple cards may be set in standby states simultaneously by monitoring control channels in turn under the control of the protocol stacks.
However, for a multi-SIM multi-standby single-communicating communication device, with only one set of communication module, while one of the SIM cards communicates with a base station through the communication module, (namely, the SIM card is conducting a communication service), the other SIM card(s) has to be waiting to receive messages on a cell's BCH (broadcast channel), such as paging messages or system messages, until the SIM card in traffic finishes its service.
FIG. 1 is a schematic diagram illustrating data reception of a traffic card and a non-traffic card in prior art. As shown in FIG. 1, the horizontal axis (T) represents time. A SIM card A starts to conduct a service (such as GSM service) at T0, and receives traffic frame on a traffic channel (TCH) until T1. In terms of GSM communication protocol, during the time period from T0 to T1, data receiving is only performed in serving cell and the neighboring cell of the SIM card which is conducting a service. After T1, both the SIM card A and SIM card B enter an idle state, paging information of the SIM card A and SIM card B may be received through Common Control Channel (CCCH). However, because the SIM card B does not receive data during the time period from T0 to T1, a gain of the SIM card B to receive data correctly is uncertain. FIG. 2 is a schematic diagram of variation of the signal gain needed for the SIM card B shown in FIG. 1 to receive data correctly. As shown in FIG. 2, the horizontal axis T represents time, and the vertical axis E represents gain. Assuming that the gain needed for the SIM card B to receive data correctly is E1 at T0 when the SIM card A starts to conduct a service, however, during the period from T0 to T1, the gain may vary due to, generally, the change of the signal intensity caused by the change of the transmission paths of the signal transmitted by a base station because of the continuous change of the position of the mobile phone. However, in terms of GSM communication protocol, the signal received is within a range, generally [−110 dBm, −47 dB] a signal with too high or too low intensity may not be received correctly, therefore, there is a need to adjust the gain of the signal. Assuming that the gain needed for the SIM card B to receive data correctly is E2 at T1 when the SIM card A finishes the service, the gain needed for the SIM card B to receive data correctly is uncertain because the SIM card B has not received data during the time period from T0 to T1 as described above. If data receiving is performed in accordance with the gain at T0, it may fail to decode data in a succession of multiple packages due to the improper gain, or even lose network connection.
Chinese patent application No. 200780000267.9 discloses a method for sending and receiving wireless signal. When quality of a user link falls below a predetermined lower limit, idle time slots on other carrier waves of the current cell, corresponding to the slots of a carrier wave initially occupied by the user, are used in diversity transmitting/receiving the user's signal. When quality of the user link surpasses a predetermined upper threshold, the time slots that the user occupies on the other carrier waves are released. In this way, the quality of the user link is improved saving network resources. However, according to the disclosure, the multi-SIM multi-standby single-communicating system has difficulty to obtain signal gains of other SIM cards for receiving data correctly when one SIM card is in a communicating state.